This invention relates to heavy medium separation.
Heavy medium separation is used extensively to separate diamond particles from gangue. The method generally involves crushing diamond-bearing ore to a predetermined size and making a suspension of the crushed mass with ferro-silicon particles in water. The suspension is pumped into a cyclone to effect separation. The tailings fraction, containing mostly gangue, issues from the top of the cyclone while the heavy fraction, containing most of the heavy minerals and diamond, issues from the bottom of the cyclone. It is difficult to determine the efficiency of the separation and it may well be that in certain cases the tailings contain considerable quantities of diamond, so much so as to justify a further separation step.
To determine the efficiency of a separation process of this type tracer elements are used. The tracer elements may be color coded according to densities. The elements correspond to a plurality of fractions, each fraction being of predetermined quantity and density. The range of densities of the fractions cover the approximate range of densities of the crushed diamond bearing ore, normally in the range of the order from 2.5 to 3.5 grams/cc.
The tracer elements are added to an aqueous suspension of the crushed ore and ferro-silicon particles and thoroughly mixed. The mixture is pumped into the cyclone and separated into a top tailings fraction and a bottom, predominantly diamond-bearing fraction. The proportion of elements of each density reporting in each fraction is then determined by counting or similar procedure and from this data appropriate distribution curves can be drawn and the efficiency of the process determined.
The tracer elements currently used are made of plastic. The plastic has a filler material of varying amounts added prior to it being extruded or otherwise formed into the tracer element. The addition of the filler material to the plastic makes it difficult to extrude the plastic into the desired tracer element.